In comparison with inorganic semiconductors such as silicon, oxide and the like, organic semiconductors are easier to fabricate, cheaper, lighter, more flexible, and more compatible with plastic substrates, therefore, they have broad applications in flexible displays, organic radio frequency identification (ORFID), organic sensors, organic solar cells, etc. (Forrest, S. R. Nature. 2004, 428, 911-918; Korzhov, M. et al. Physics Word. 2008, 29-33; Leenen, M. A. M. et al. Phys. Status Solidi A. 2009, 206, 588-597; Special issue: Organic Electronics and Optoelectronics, Forrest, S. R.; Thompson, M. E. ed. Chem. Rev. 2007, 107, 923-1386 etc.) Along with the development in techniques related to organic semiconductors and devices, thin, portable, flectional, wearable and fashionable organic electronic products will gradually emerge in our daily life, and bring revolutionary transformation to the electronics industry and the life of human beings.
Organic semiconductors, which are the key components of organic electronic devices, can be classified based on their transport carriers into two categories, p-type organic semiconductor/organic donor (hole-transporting), and n-type organic semiconductor/organic acceptor (electron-transporting). In general, the development of p-type organic semiconductor/organic donor is more advanced. The performance of certain organic thin-film transistors (OTFTs) of solution-processable molecular material is comparable to that of amorphous silicon (McCulloch, I. et al. Nat. Mater. 2006, 5, 328-333; Ebata, H. et al. J. Am. Chem. Soc. 2007, 129, 15732-15733; Osaka, I. et al. J. Am. Chem. Soc. 2010, 132, 5000-5001). The photoelectric conversion efficiency of certain D-A structure polymeric donor and organic acceptor (PCBM, a fullerene derivative) constructed heterojunction organic solar cell reaches 7.4% (Liang, Y. et al. Adv. Mater. 2010, 22, E135-E138). In the field of OTFTs, n-type organic semiconductors play a critical role in constructing organic p-n junction diodes, ambipolar transistors, and complementary circuits with low power consumption and high noise margin (Newman, C. R. et al. Chem. Mater. 2004, 16, 4436-4451; Klauk, H. et al. Nature. 2007, 445, 745-748; Yan, H. et al. Nature. 2009, 457, 679-686). In the field of organic photovoltaics (OPV), n-type organic semiconductors (organic acceptors) broadly applied in bulk heterojunction organic solar cells are primarily confined within fullerene derivatives (such as PCBM, etc.); organic semiconducting sensitizers used in organic sensitized solar cells are primarily p-type organic semiconductors (Odobel, F. et al. Acc. Chem. Res. 2010, 43, 1063-1071). Therefore, the n-type organic semiconductor/organic acceptor, although slowly developing, have becoming the technical bottleneck to the advancing of organic electronics.
Naphthalenetetracarboxylic acid diimide (NDI) is a typical class of n-type organic semiconductors which are widely used in the fabrication of n-type OTFT devices. However, its relatively small conjugated aromatic ring makes it difficult to form an efficient π-π stacking in a solid structure, and the resulting OTFT devices exhibit a relatively low electron mobility; on the other hand, NDI-based OTFT devices fabricated by solution process are quite rare, with the poor film-forming ability and poor device performance. For the seeking of n-type organic semiconductors with high electron mobility, better environmental stability and manufactural easiness, the inventors report five classes of sulfur containing heterocycle-fused naphthalenetetracarboxylic acid diimides (CN200910197611.9, priority date of Oct. 23, 2009; CN201010207565.9, priority date of Jun. 23, 2010): 2-(1,3-dithiacyclopenten-2-ylidene)-2-malononitrile fused naphthalenetetracarboxylic acid diimide derivatives, alkyl 2-(1,3-dithiacyclopenten-2-ylidene)-2-cyanoacetate fused naphthalenetetracarboxylic acid diimide derivatives, 2-(1,3-dithiacyclopenten-2-ylidene)-2-phenyl acetonitrile fused naphthalenetetracarboxylic acid diimide derivatives, 1,4-dithiacyclohexadiene-2,3-dicarbonitrile fused naphthalenetetracarboxylic acid diimide derivatives and α,β-dicyanothiophene fused naphthalenetetracarboxylic acid diimide derivatives, the applications of some such compounds in OTFT devices are also disclosed.